1. Field of the Invention
The present invention relates generally to disk drives and in particular to tooling mandrels for assembling disk drives, and methods of assembling disk drives using the same.
2. Description of the Related Art
The typical hard disk drive includes a head disk assembly (HDA) and a printed circuit board assembly (PCBA) attached to a disk drive base of the HDA. The head disk assembly includes at least one magnetic disk, a spindle motor for rotating the disk, and a head stack assembly (HSA). The spindle motor includes a spindle motor hub that is rotatably attached to the disk drive base.
The head stack assembly has an actuator assembly having at least one transducer head, typically several, for reading and writing data from and to the disk. The printed circuit board assembly includes a servo control system in the form of a disk controller for generating servo control signals. The head stack assembly is controllably positioned in response to the generated servo control signals from the disk controller. In so doing, the attached heads are moved relative to data tracks disposed upon the disk.
In further detail, the head stack assembly includes an actuator assembly, at least one head gimbal assembly, and a flex circuit cable assembly. A conventional “rotary” or “swing-type” actuator assembly typically includes an actuator having an actuator body. The actuator body is configured to rotate on a pivot assembly between limited positions about an axis of rotation. The pivot assembly includes a pivot bearing cartridge that has a shaft, a sleeve disposed about the shaft, and bearings disposed there between. A coil support extends from one side of the actuator body, and a coil is supported by the coil support. The coil is configured to interact with one or more permanent magnets to form a voice coil motor. Energizing the coil results in forces that tend to pivot the actuator. A change in the direction of current through the coil results in a change in the resulting pivot direction.
One or more actuator arms extend from an opposite side of the actuator body. To facilitate rotational movement of the actuator, the actuator assembly further includes the actuator body that has a bore and a pivot bearing cartridge engaged within the bore. Each magnetic disk includes opposing disk surfaces. Data may be recorded on a single surface or both surfaces along annular data regions. As such, the head stack assembly may be pivoted such that each transducer head is disposed adjacent the various annular data regions.
A topic of concern is the assembly process in regards to the head stack assembly. Engagement of a head stack assembly with a disk drive base may begin with a “pick and place” operation. This involves picking up a head stack assembly from its storage location and placing it upon a disk drive base at an assembly station. This may be done either manually or through the use of an automated device, such as a “pick and place” robotic armature.
The shaft of the pivot bearing cartridge may be slightly asymmetrical. Such slight asymmetrical nature may result in an axial run-out phenomenon that manifests itself as inconsistent performance from one disk drive to the next. As such, it is desirable to consistently install the head stack assemblies at a consistent angular disposition with respect to their respective disk drive bases. During installation, once the head stack assembly is disposed in the disk drive base, a separate tool may be used to orient the shaft at a predetermined angle. This may be done either manually or through the use of an automated device located at the assembly station. Finally, the head stack assembly is attached to the disk drive base. For example, a fastener may be used to attach the shaft of the pivot bearing cartridge to the disk drive base. This also may be done either manually or through the use of an automated device located at the assembly station. However, to grasp the shaft of the pivot bearing cartridge and to prevent it from rotating when the fastener (typically a screw) is tightened, the robotic armature conventionally grasps the outer diameter of the shaft, while a screw-driver-shaped member engages a slot formed in the shaft to counter the angular forces imposed upon the shaft when the screw is tightened. This prevents the shaft from rotating away from its predetermined orientation during the screw driving step. Conventionally, the slot defined within the shaft of the pivot bearing cartridge extends across the entire diameter of the shaft.
However, recent design constraints have rendered this orientation stabilization method less than optimal. Such design changes have included moving the inner race of the top ball bearing assembly closer to the slot defined within the shaft. Therefore, the screw driver-shaped member that engaged the slot defined within the top portion of the shaft of the pivot bearing cartridge risks damaging the inner race of the top ball bearing assembly, which may, in turn, exacerbate the effects of above-mentioned axial run-out phenomenon. As such, there is a need in the art for improved tools and methods for assembling disk drives, and for preventing other problems, such as contamination brinelled bearings, frozen bearings, etc.